1. Field of the Invention
The present invention relates to a material for forming a protective film that is embedded in a hole pattern, when a multilayered wiring structure is formed.
2. Description of the Related Art
In recent years, with increased integration of semiconductor elements and a reduction of chip size, development of fine and multilayered wiring has been progressing. Under the circumstances, the size of a hole pattern that is formed by photolithography techniques is further miniaturized.
To form such a miniaturized hole pattern, use of metal such as Cu has been proposed, and therewith lithography techniques have been applied, in which the Damascene method or the Dual Damascene method is used.
In the Dual Damascene method, when upper wiring is formed after formation of a hole pattern, it is necessary to embed the hole pattern once to protect lower wiring from damage due to etching. It has been proposed that a photoresist composition is used as a material for forming the protective film.
However, the above described photoresist composition has a disadvantage in that an air bubble that is called “void” generates when the composition is embedded in a via hole with a large aspect ratio.
To solve the above problem, Japanese Patent Application Laid-Open (Kokai) No. 2000-195955 discloses embedding materials wherein a thermal crosslinking compound such as a melamine derivative or benzoguanamine derivative is used. The embedding feature and flatness of these embedding materials have been improved when compared with those of photoresist compositions, but the feature and the flatness have not satisfied yet the features that are required today.